Postage meters are mass produced devices for printing a defined unit value for governmental or private carrier delivery of parcels and envelopes. The term "postage meter" also includes other like devices which provide unit value printing such as "tax stamp meters". Postage meters conventionally include internal accounting devices which account for postage value representation which is stored within the meter and is printed by the meter. As a result, postage meters must possess a high degree of reliability to avoid the loss of user or governmental funds stored within the meter.
Electronic postage meters have been developed. Postage meter systems of this type are disclosed in U.S. Pat. Nos. 3,978,457 for Microcomputerized Electronic Postage Meter System; and in 4,301,507 for Electronic Postage Meter Having Plural Computing Systems. Such meters may have electronic accounting circuits which include non-volatile memory capability for storing postage accounting information. The memory functions in these electronic accounting circuits have replaced the function served in mechanical postage meters by mechanical accounting registers.
Systems have been developed where encryption is employed in the imprinting of postage such as is disclosed in U.S. patent application Ser. No. 724,372, filed Apr. 17, 1985 for George B. Edelmann and Arno Muller and entitled "System for Detecting Unaccounted for Printing in a Value Printing System" and is a continuation in part U.S. patent application Ser. No. 832,904 filed Feb. 25, 1986 for George B. Edelmann, Arno Muller, Alfred Schmidt and Kevin Hunter and also entitled "System for Detecting Unaccounted for Printing in a Value Printing System." These systems involve the printing of encrypted information on a mailpiece to provide an indication of the validity of the imprint on the mailpiece. These systems employ accounting circuitry which is resident in the meter at the user location.
A system is disclosed in U.S. patent application Ser. No. 882,871, filed concurrently herewith, for Wojciech M. Chrosny and entitled "Postage Payment System Employing Encryption Techniques and Accounting for Postage Payment at a Time Subsequent to the Printing of the Postage." This system discloses the basic concept of accounting for postage at a time subsequent to the printing of postage and a system wherein no secure postage accounting takes place and no postage funds are stored within the meter at the postage user location.